Forum-based user mention alerts

Simple, anytime someone mentions another user by name anywhere in the forums, that user gets alerted via notifications with a link to the post in question. Doesn't subscribe to the thread the mention occurred in, unless that user decides to respond.

Would probably have to be exact spelling at least, and if someone's username had a non-alpha-numeric character then it shouldn't matter if it was typed or not.

Could also work on the chat since logs are kept, though I'm not sure how useful such information would be. By the time someone was aware he or she was part of a conversation it would likely be long over.

Much less critical would be a dialog that suggested users as your typing.